Isomer-specific degradation and endocrine disrupting activity of nonylphenols

Gabriel, F. L. P.; Heidlberger, A.; Rentsch, D.; Sumpter, J.P.; Giger, W.; Kohler, H.-P.E.; Routledge, E.J.; Günther, K.

doi:10.1021/es800577a

Journal Article

Isomer-specific degradation and endocrine disrupting activity of nonylphenols

Gabriel, F. L. P. ; Routledge, E. J. ; Heidlberger, A. ; Rentsch, D. ; Günther, K.FZJ* ; Giger, W. ; Sumpter, J. P. ; Kohler, H.-P.

2008
American Chemical Society Columbus, Ohio

Environmental Science & Technology 42, 6399 - 6408 (2008) [10.1021/es800577a]

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Please use a persistent id in citations: http://hdl.handle.net/2128/25412 doi:10.1021/es800577a

Abstract: Degradation of technical nonylphenol by Sphingobium xenophagum Bayram led to a significant shift in the isomers composition of the mixture. By means of gas chromatography-mass spectrometry, we could observe a strong correlation between transformation of individual isomers and their a-substitution pattern, as expressed by their assignment to one of six mass spectrometric groups. As a rule, isomers with less bulkiness at the a-carbon and those with an optimally sized main alkyl chain (4-6 carbon atoms) were degraded more efficiently. By mass spectrometric analysis, we identified the two most recalcitrant main isomers of the technical mixture (Group4) as 4-(1,2-dimethyl-1-propylbutyl) phenols (NP193a and NP193b, which are diastereomers with a bulky alpha-CH3, alpha-CH(CH3)C2H5 substitution. Our experiments with strain Bayram show that the selective enrichment of isomers with bulky a-substitutions observed in nonylphenol fingerprints of natural systems can be caused by microbial ipso-hydroxylation. Based on the yeast estrogen assay (YES), we established an estrogenicity ranking with a variety of single isomers and compared it to rankings obtained with different reporter cell systems. Structure-activity relationships derived from these data suggest that Group 4 isomers have a high estrogenic potency. This indicates a substantial risk that enrichment of highly estrogenic isomers during microbial degradation by ipso-substitution will increase the specific estrogenicity of aging material.

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Note: This research was supported by the Swiss National Science Foundation within the framework of the National Research Programme NFP50 "Endocrine Disruptors: Relevance to Humans, Animals, and Ecosystems". We thank Dr. Ian Purvis and others at GlaxoSmithKline for kindly supplying the genetically modified yeast strain.

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